Insertion tool for Inter-body Vertebral Prosthetic Device With Self-Deploying Screws

ABSTRACT

An apparatus for inserting an intervertebral prosthesis within a spine of a mammal includes: a handle disposed at a proximal end of the tool and including a drive nut operating to produce rotational torque in response to user-input about a central axis; a first drive shaft including proximal and distal ends; the proximal end in communication with the drive nut, receiving rotational torque therefrom, and imparting rotational torque to the first drive shaft about a first axis, which is laterally offset from the central axis; and the distal end of the first drive shaft including a first drive head; and a chuck disposed at a distal end of the tool and being sized and shaped to engage the intervertebral prosthesis during implantation, wherein the first drive shaft extends through the chuck and the first drive head engages a first gear of the intervertebral prosthesis, such that rotation of the first gear causes rotation and deployment of a first anchoring element of the intervertebral prosthesis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 12/339,766, filed Dec. 19, 2008, now pending, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND

The present disclosure generally relates to apparatus and methods fortreatment of spinal disorders using an intervertebral prosthesis whichis disposed in an intervertebral space (or cavity) following removal ofa damaged or diseased intervertebral disc.

The bones and connective tissue of an adult human spinal column consistsof more than twenty discrete bones coupled sequentially to one anotherby a tri-joint complex. Each tri-joint complex includes an anterior discand two posterior facet joints. The anterior space between adjacentbones are cushioned by cartilage spacers referred to as intervertebraldiscs. These more than twenty bones are anatomically categorized asbeing members of one of four classifications: cervical, thoracic,lumbar, or sacral. The cervical portion of the spine, which comprisesthe top of the spine, up to the base of the skull, includes the firstseven vertebrae. The intermediate twelve bones are the thoracicvertebrae, and connect to the lower spine comprising the five lumbarvertebrae. The base of the spine includes the sacral bones (includingthe coccyx). The component bones of the cervical spine are generallysmaller than those of the thoracic spine, which are in turn smaller thanthose of the lumbar region. The sacral region connects laterally to thepelvis.

The spinal column is highly complex in that it includes these more thantwenty bones coupled to one another, housing and protecting criticalelements of the nervous system having innumerable peripheral nerves andcirculatory bodies in close proximity. In spite of these conditions, thespine is a highly flexible structure, capable of a high degree ofcurvature and twist in nearly every direction.

Genetic or developmental irregularities, trauma, chronic stress, tumors,and degenerative wear are a few of the factors that can result in spinalpathologies for which surgical intervention may be necessary. A varietyof systems have been disclosed in the art that achieve immobilizationand/or fusion of adjacent bones by implanting artificial assemblies inor on the spinal column. The region of the back that needs to beimmobilized, as well as the individual variations in anatomy, determinesthe appropriate surgical protocol and implantation assembly. The spinesurgical community has accepted intervertebral devices (commonly knownas interbody spacers, and allograft transplants) as part of the state ofthe art and routine practice employs such devices in the reconstructionof collapsed inter-vertebral disc spaces.

Surgeons insert these intervertebral devices to facilitate bone fusionin between and into the contiguous involved vertebrae. This fusioncreates a new solid bone mass, which acts to hold the spinal segment atan appropriate biomechanically restored height as well as to stop motionin a segment of the spine in which the patient is experiencing pain.Items surgically placed in these involved interbody regions can thusstimulate interbody bone in-growth such that the operated anteriorspinal segments heal into a contiguous bone mass; in other words, afusion occurs. Further, the surgical community uses such man-madeimplants or biological options to provide weight bearing support betweenadjacent vertebral bodies, and thereby correct or alleviate a variety ofclinical problems. In this regard, surgeons use intervertebral spinalimplants/transplants for surgical therapy for degenerative disc disease(DDD), discogenic low back pain, spondylolisthesis, reconstructionfollowing tumor or infection surgery, and other spine related maladiesrequiring surgical intervention.

In many implant designs, a relatively hard or sturdy implant constructis formed from a selected biocompatible material such as metal, ceramic,or carbon fiber-reinforced polymer. This implant construct often has apartially open or porous configuration and is coated or partially filledwith a selected bone ingrowth-enhancing substance, such as harvestedbone graft supplied from the patient, human donor allograft bonetransplant material supplied by a tissue bank, genetically cultivatedbone growing protein substitutes, and/or other biological/biochemicalbone extenders. Such devices, when implanted into the intervertebralspace, promote ingrowth of blood supply and grow active and live bonefrom the adjacent spinal vertebrae to inter-knit with the implant,thereby eventually immobilizing or fusing the adjacent spinal vertebrae.Such implants also commonly include a patterned exterior surface such asa ribbed or serrated surface, or screw thread geometry, to achieveenhanced mechanical locking with the adjacent vertebrae during the boneingrowth/fusion process.

With respect to the failure of the intervertebral disc, the interbodyfusion cage has generated substantial interest because it can beimplanted laparoscopically into the anterior of the spine, thus reducingoperating room time, patient recovery time, and scarification.Conventional intervertebral body cages generally comprise a tubularmetal body having an external surface threading. They are insertedtransverse to the axis of the spine, into preformed cylindrical holes atthe junction of adjacent vertebral bodies. The cages include holesthrough which the adjacent bones are to grow. Additional materials, forexample autogenous bone graft materials, may be inserted into the hollowinterior of the cage to incite or accelerate the growth of the bone intothe cage.

There are several commercially available devices that operate asstand-alone (that is, without support from an additional construct suchas an anterior plate and screws, or posteriorly placed screws and/orrods placed into the pedicles or facet joints) interbody fusion devices.These devices include the Stalif™, SynFix™, and the VerteBridge™. TheStalif™ is a device for the fusion of the lumbar spine. The implant isinserted and fixed via diverging screws passing through pre-drilledapertures of the device that penetrate into the vertebral bodies. Thescrews are manually placed into the apertures of the device and aredriven using an appropriate tool, such as a surgical screw driver. TheStalif™ is available from Surgicraft Limited Corporation, 16 The OaksClews Road Redditch, United Kingdom (www.surgicraft.co.uk). The SynFix™is also a device that is placed in an intervertebral space and fixed viadiverging screws passing through the device and into the vertebralbodies. Again, the screws are manually placed into the apertures of thedevice and are driven using a surgical screw driver. The SynFix™ isavailable from Synthes, Inc., 1302 Wrights Lane East, West Chester, Pa.19380 (www.synthes.com). The VerteBridge™ is a device for the fusion ofthe spine in which anchoring blades are press-driven (using aspecialized tool) through apertures in the device and into therespective vertebral bodies to fix the device in place. The VerteBridge™is available through the LDR Spine (www.ldrholding.com).

All of the above-described devices have an anchor which is secondarilyadded to the initial device. The Stalift™ and SynFix™ devices employscrews while the VerteBridge™ utilizes a blade anchor. Both the Stalif™and SynFix™ devices require the screws to be inserted at trajectoriesthat are difficult to achieve given common human anatomical structures,especially at the spinal level L5-S1. Additionally, the proximal end ofthe screws may protrude anteriorly, causing potential irritation to thegreat vessels. The VerteBridge™ has a pair of blades inserted after theinitial device is put in place. The blades are supposed to flex enoughto curve within the device, and to exhibit sufficient strength to cutthrough bone. These blades, although flexible, need to be able to holdthe vertebral bodies in place. In practice, these features are notalways achieved.

A number of devices have been developed, which employ self-containedanchoring elements that are deployed after the device is placed into theintervertebral space. For example, U.S. Patent Application Pub. No.2006/0241621 (incorporated herein in its entirety) discloses a devicefor joining intervertebral members together using a self-drilling screwapparatus. The screw apparatus includes a shell and first and secondscrew members having tapered ends and threaded bodies that are disposedwithin the shell. A drive mechanism rotatably drives the first andsecond screw members from the shell in precisely co-axial, oppositedirections, which causes the screw members to embed themselves in thevertebral bodies. U.S. Pat. No. 5,800,550 (incorporated herein in itsentirety) discloses a device for joining intervertebral members togetherusing a self-deploying pair of posts. The apparatus includes a body andfirst and second post members that are disposed within the body. A drivemechanism press-drives the first and second posts from the body inprecisely co-axial, opposite directions (longitudinally aligned with thespine), which causes the posts to embed themselves in the vertebralbodies. The problems with these devices include that the co-axial,opposite deployment of the screws/posts is not an ideal configurationfor fixing an intervertebral device. Indeed, such a deployment maypermit slippage of the device during or after deployment because of thenatural stresses applied to the device from the patient's anatomicalspinal structures.

Given the disadvantageous features of the prior art devices, there is aneed for a new intervertebral device that includes self-containedanchoring members that deploy in desirable transverse directions, aswell as instrumentation for inserting the device in a patient's spine.

SUMMARY OF THE INVENTION

Embodiments of the present invention are stand-alone interbody devices,which may be designed in the general style of an anterior lumbarinterbody fusion (ALIF) device, a transforaminal lumbar interbody fusion(TLIF) device, a posterior lumbar interbody fusion (PLIF) device, anextreme lateral or direct lateral interbody device fusion device, or acervical interbody device.

The device includes a body made from any variety of structuralbiomaterial including, but not limited to, polyetheretherketone (PEEK),Titanium, ceramic, etc. The body may have serrated superior and/orinferior surfaces to provide initial resistance against migration.Additionally, there may be at least one opening extending from thesuperior surface to the inferior surface for the purpose of containingosteo-inductive material, such as autograft, bone morphogenetic protein(BMP), bone marrow aspirate, etc.

The body contains at least one screw therein, which screw may bedeployed from the body of the device via a gear drive in a transversedirection with respect to a normal axis of the device. In one or moreembodiments, there may be one or more holes on an anterior face of thebody for engagement with an inserter device. One or more of the holesmay also serve as the openings for a gear drive engagement tool tooperate the gear and deploy the at least one screw from the body.

The gear drive is disposed within the body of the device and includesteeth that mesh with, and interact with, the threads of the one or morescrews such that turning the gear turns the screws, thereby deployingsame from the body. Thus, the gear drives the one or more screws intothe vertebral bodies, securing the device in place. The gear may bedriven via a driver, preferably on an inserter for the device itself.After deployment of the one or more screws from the body into thevertebral bodies, the gear may be locked into place via a set screw(although any other known or hereinafter developed methods may also beused to secure the gear).

The screws of the device are initially hidden within the body. Thisallows for the device to be easily inserted within the disc spacewithout the screws protruding. The screws must be self-drilling andself-tapping in order to cut into the vertebral body bone. Two or morescrews may be driven by one gear, which may require different threadgeometry than a single screw configuration, such as one screw having aleft-handed thread, the other screw having a right-handed thread. Thescrew may have a larger diameter on the proximal end (the end remainingin the body of the device), such that the screw may engage the vertebralbody at a specified point, yet restricting deployment of the screw fromthe device such that the screw is prevented from completely exiting thedevice.

One of the benefits of the embodiments of the invention is the ease withwhich the device may be used. There are fewer steps as compared withconventional devices because all of the screws can be deployed from thebody of the device using the same tool from inserting the device intothe intervertebral space. Furthermore, because the screws areself-contained, there is no difficult trajectory needed to place thescrews as with previous devices. As opposed to devices employing bladesor posts, the embodiments of the invention employ screws, which providebetter fixation and stabilization. Because screws can be deployed in avariety of angles, they can provide better fixation.

In accordance with one or more embodiments of the present invention, anintervertebral prosthesis, includes: a body including first and secondspaced apart major surfaces and at least anterior and posteriorsidewalls extending therebetween, the first major surface for engagingan endplate of a first vertebral bone of a spine, and the second majorsurface for engaging an endplate of an adjacent, second vertebral boneof the spine, and the first and second major surfaces defining alongitudinal axis extending substantially normal to said surfaces; afirst aperture extending from within the body, transversely with respectto the longitudinal axis, and opening at the first major surface; afirst anchoring element disposed within the first aperture and includinga threaded shaft having proximal and distal ends; and a first geardisposed adjacent to and in meshed, threaded communication with thethreaded shaft of the first anchoring element such that rotation of thefirst gear causes rotation of the first anchoring element.

A driving rotational force on the first gear causes the first anchoringelement to rotate, deploy from the body, and thread into the firstvertebral bone in a direction transverse to the longitudinal axis of thebody and the spine.

In accordance with one or more aspects of the present invention, anapparatus for inserting an intervertebral prosthesis within a spine of amammal may include: a handle disposed at a proximal end of the tool andincluding a drive nut operating to produce rotational torque in responseto user-input about a central axis; and a first drive shaft includingproximal and distal ends; the proximal end in communication with thedrive nut, receiving rotational torque therefrom, and impartingrotational torque to the first drive shaft about a first axis, which islaterally offset from the central axis; and the distal end of the firstdrive shaft including a first drive head. The first drive head mayengage a first gear of the intervertebral prosthesis, such that rotationof the first gear causes rotation and deployment of a first anchoringelement of the intervertebral prosthesis.

Additionally, the apparatus may further include a second drive shaftincluding proximal and distal ends, the proximal end being incommunication with the drive nut, receiving rotational torque therefrom,and imparting rotational torque to the second drive shaft about a secondaxis. The second axis may be laterally offset from both the central axisand the first axis. The distal end of the second drive shaft includes asecond drive head, wherein the second drive head operates to engage asecond gear of the intervertebral prosthesis, such that rotation of thesecond gear causes rotation and deployment of a second anchoring elementof the intervertebral prosthesis.

The apparatus may further include a main drive gear rotatable about acentral axis, and coupled to, and receiving the rotational torque from,the drive nut. The first and/or second drive shaft may include a pickupgear in meshed communication with the main drive gear, receivingrotational torque therefrom, and imparting rotational torque to therespective drive shaft.

Other aspects, features, advantages, etc. will become apparent to oneskilled in the art when the description of the preferred embodiments ofthe invention herein is taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purposes of illustrating the various aspects of the invention,there are shown in the drawings forms that are presently preferred, itbeing understood, however, that the invention is not limited to theprecise arrangements and instrumentalities shown.

FIG. 1 is a perspective view of an intervertebral prosthetic device inaccordance with one or more embodiments of the present invention;

FIG. 1B is a side view of the intervertebral device of FIG. 1;

FIGS. 2A-2B are illustrations of the intervertebral device of FIG. 1 inuse;

FIG. 3A is a perspective view of the intervertebral prosthetic devicewith anchoring elements deployed;

FIG. 3B is a side view of the intervertebral device of FIG. 3;

FIG. 4 is a cut-away perspective view of the intervertebral prostheticdevice of FIG. 3A showing an example of the inner construction of thedevice;

FIG. 5A is a perspective view of an intervertebral prosthetic device inaccordance with one or more alternative embodiments of the presentinvention;

FIG. 5B is a cut-away perspective view of the intervertebral prostheticdevice of FIG. 5A showing an example of the inner construction of thedevice;

FIG. 6 is a perspective view of an intervertebral prosthetic device inaccordance with one or more alternative embodiments of the presentinvention;

FIG. 7 is a side view of the intervertebral device of FIG. 6;

FIG. 8 is a cut-away perspective view of the intervertebral prostheticdevice of FIG. 6 showing an example of the inner construction of thedevice;

FIG. 9 is a front view of the intervertebral device of FIG. 6;

FIG. 10 is a perspective view of an intervertebral prosthetic device inaccordance with one or more alternative embodiments of the presentinvention;

FIG. 11 is a front view of the intervertebral device of FIG. 10;

FIG. 12 is a cut-away perspective view of the intervertebral prostheticdevice of FIG. 10 showing an example of the inner construction of thedevice;

FIGS. 13A and 13B are side and top views, respectively, of a tool forinserting an intervertebral prosthetic device in accordance with one ormore further aspects of the present invention;

FIG. 14 is an exploded view of a proximal end of the tool of FIGS. 13Aand 13B;

FIG. 15 is an exploded view of a distal end of the tool of FIGS. 13A and13B;

FIG. 16 is a sectional view of the tool of FIG. 13A, taken through line16-16;

FIG. 17 is an enlargement of a distal end of the sectional view of FIG.16;

FIG. 18 is an enlargement of a proximal end of the sectional view ofFIG. 16; and

FIG. 19 is an end view of the tool of FIGS. 13A and 13B showingalternative or additional features in accordance with one or morefurther aspects of the invention.

DETAILS OF THE EMBODIMENTS OF THE INVENTION

Reference is now made to FIGS. 1A and 1B, which illustrate anintervertebral prosthetic device 100 in accordance with one or moreembodiments of the present invention. FIG. 1A illustrates a perspectiveview of the intervertebral device 100, while FIG. 1B is a lateral (side)view with the left of the drawing being in the front (anterior)direction and the right of the drawing being in the rear (posterior)direction. The body of the device may be made from any bio-compatiblematerial, such as polyetheretherketone (PEEK), titanium, ceramic, etc.

With further reference to FIG. 2A, which shows the device 100 in use,the device 100 generally includes a body (or housing) that is sized andshaped to fit in the intervertebral space between adjacent vertebralbones 10, 20 of the human spine. It is understood that the size andshape of the device 100 may be adapted to fit in an intervertebral spaceat any level of the spine, such as the cervical spine, thoracic spine,or lumbar spine. The intervertebral device 100 as illustrated in thisexample is designed to be a stand-alone device (e.g., requiring noseparate anchoring devices), which is inserted into the inter-vertebralspace from an anterior direction. This embodiment is in the general formof an ALIF device, although as will be appreciated from the descriptionherein, the device may be adapted to operate as a TLIF device, extremelateral or direct lateral interbody device, PLIF device, or a cervicalinterbody device.

The body includes first and second spaced apart major surfaces 102, 104and anterior and posterior sidewalls 106, 108 extending therebetween.The first major surface 102 operates to engage an endplate of the firstvertebral bone 10 of the spine, and the second major surface 104operates to engage an endplate of the adjacent, second vertebral bone 20of the spine. As best seen in FIGS. 1B and 2A, the first and secondmajor surfaces 102, 104 define a longitudinal axis Lo extendingsubstantially normal to said surfaces and either coaxial with, orgenerally parallel to, the longitudinal direction of the spine. Withreference to FIG. 1B, it is understood that the longitudinal axis Lo isnot precisely normal to the first and second major surfaces 102, 104 asthere is a slight narrowing height (taper) to the body from the anteriorsidewall 106 to the posterior sidewall 108. This taper is designed toaccommodate the natural anatomic relationships between the adjacentvertebral bones 10, 20, thereby maintaining the normal lordodiccurvature of the spine.

The surgery involved with implanting the device 100 involves removal ofthe disc material from the intervertebral space, release of thecontracted soft tissues around the disc space, and some degree ofdistraction or pulling apart of the adjacent vertebrae 10, 20 in anattempt to restore disc space height, realign the spine, and indirectlydecompress the nerve roots exiting the spine posteriorly at theparticular level. After the surgeon removes the disc material, a cleanaperture (space) is achieved in which to place the device 100. Thesurgeon may use a tool to simultaneously grasp the body of the device100, place it at the mouth of the intervertebral space, and apply forceso that the device 100 achieves its final placement.

In order to facilitate desirable adhesion between the endplates of therespective vertebral bones 10, 20 and the device 100, one or both of thefirst and second major surfaces 102, 104 of the body include a boneengagement feature, such as at least one of serrations, protrusions,valleys, spikes, knurling, keels, etc. Additionally or alternatively,the intervertebral prosthesis 100 may include one or more apertures 110extending between and through at least one of the first and second majorsurfaces 102, 104 of the body that operate to permit osteo-inductivegrowth between the body of the prosthesis 100 and the one or morevertebral bones 10, 20.

As illustrated in FIG. 2B, once the surgeon has manipulated the device100 into its proper orientation within the intervertebral space, one ormore anchoring elements 120A, 120B, such as threaded screws, aredeployed from within the body and engage one or more of the vertebralbones 10, 20. As will be described in more detail herein, the anchoringelements 120A, 120B deploy from the body and thread into the vertebralbones 10, 20 in directions transverse to the longitudinal axis Lo of thebody and the spine.

With reference to FIGS. 1A, 3A, and 3B, the body of the device includesat least a first aperture 122A extending from within the body,transversely with respect to the longitudinal axis Lo, and opening atthe first major surface 102. A first anchoring element 120A is disposedwithin the first aperture 122A in a manner in which deployment of theanchoring element 120A results in a trajectory out of the body and intothe given vertebral bone in a direction transverse to the longitudinalaxis Lo of the body and the spine. Preferably, the anchoring element120A is in the form of a threaded shaft having a proximal end and adistal end 124A. Preferably, the distal end 124A and the threads of thefirst anchoring element 120A are of a self-drilling and self-tappingconstruction.

The first aperture 122A may be characterized by smooth walls that permitthe anchoring element 120A to rotate and translate therethrough duringdeployment. Alternatively, the first aperture 122A may be characterizedby a thread, which matches that of the threaded shaft of the firstanchoring element 120A. When the wall of the first aperture 122A isthreaded, the rotation of the first anchoring element 120A causes thethreads thereof to advance the first anchoring element 120A into thevertebral bone during deployment.

With reference to FIG. 3B, the trajectory Lt of the anchoring element120A is of importance to achieving desirable fixation of the device 100within the intervertebral space and avoidance of later migration duringuse. In this regard, the direction of the first aperture 122A, and thusthe direction Lt of deployment of the anchoring element 120A therefrom,is transverse to the longitudinal axis Lo of the body. Moreparticularly, the deployment direction Lt includes a first substantialdirectional component La in an anterior direction of the body (towardthe anterior sidewall 106). The deployment direction Lt also includes asecond substantial directional component Lp parallel to the longitudinalaxis Lo of the spine. These components of trajectory, Lt=La+Lp, in theanterior and longitudinal directions characterize a significantdifference with prior art techniques, where the deployment is fully inthe longitudinal direction of the spine.

Although various embodiments of the invention may include a singleanchoring element, it is preferred that the device 100 include aplurality of anchoring elements 120, such as including at least a secondanchoring element 120B. In this regard, the body of the device 100 mayinclude at least a second aperture 122B extending from within the body,transversely with respect to the longitudinal axis Lo, and opening atthe second major surface 104. The second anchoring element 120B may bedisposed within the second aperture 122B in a manner in which deploymentof the anchoring element 120B results in a trajectory into the givenvertebral bone 20 in a direction −Lt transverse to the longitudinal axisLo of the body and the spine. Preferably, the anchoring element 120A isin the form of a threaded shaft having a proximal end and a distal end124A. The structural characteristics of the second anchoring element120B and the second aperture 122B include the options previouslydiscussed with respect to the first anchoring element 120A and firstaperture 122A.

Again, the trajectory −Lt of the anchoring element 120B is of importanceto achieving desirable fixation of the device 100 within theintervertebral space. The direction of the second anchoring element 120Btransverse to the longitudinal axis Lo of the body includes a firstsubstantial directional component La in the anterior direction of thespine, and a second substantial directional component −Lp parallel tothe longitudinal axis Lo of the spine, but opposite to the secondsubstantial directional component Lp of the first anchoring element120A. The transverse and opposite trajectories of the first and secondanchoring elements 120A, 120B provide significant improvement inanchoring strength (e.g., improved resistance to sheer stress) ascompared with prior art devices.

The anchoring characteristics of the device 100 within theintervertebral space may be adjusted by adding or removing any number ofindividual anchoring elements 120. In one or more embodiments, such asthe device 100 of FIGS. 1A-3B, a first pair of anchoring elements 120A,120B may be disposed at one lateral side of the body, and a second pairof anchoring elements 120C, 120D (of similar construction) may bedisposed at another opposite lateral side of the body. In thisembodiment, each of the anchoring elements 120 exhibits a deploymenttrajectory having a substantial component ±La in the anterior direction.

Reference is now made to FIG. 4, which illustrates one example of how toimplement the deploying anchoring element(s) 120 of the device 100. Inparticular, the device 100 may include a first gear 130A disposed withina first gear aperture 132A. The first gear 130A is disposed adjacent to,and in meshed, threaded communication with, the threaded shaft of thefirst anchoring element 120A. The first gear aperture 132A and the firstaperture 122A for the first anchoring element 120A are located andoriented such that the apertures intersect over at least a portionthereof, and such that the first anchoring element 120A and the firstgear 130A are in meshed, threaded communication at the intersection.

In the illustrated example, the first gear 130A is in the form of a wormgear having a longitudinal orientation in an anterior-posteriordirection within the first gear aperture 132A. In this embodiment, thelongitudinal orientation of the first gear 130A may be substantiallyparallel to the first and second major surfaces 102, 104 of the body.Those skilled in the art will appreciate that the threads of the firstgear 130A and the threads of the first anchoring element 120A may bereadily sized and shaped (in terms of pitch, depth, profile, etc.) suchthat rotation of the first gear 130A causes rotation of the firstanchoring element 120A.

Although various embodiments of the invention may include one anchoringelement in communication with the first gear 130A, it is preferred thatat least two anchoring elements are in communication with the first gear130A. Thus, the first gear aperture 132A is located and oriented suchthat the first gear 130A is also disposed adjacent to, and in meshed,threaded communication with, the threaded shaft of the second anchoringelement 120B. The first gear aperture 132A intersects, over at leastportions thereof, with each of the first and second apertures 122A, 122Bsuch that the first gear 130A is in meshed, threaded communication atthe intersection with each of the first and second anchoring elements120A, 120B. As best seen in FIG. 4, the intersection of the first gearaperture 130A, the first aperture 122A, and the second aperture 122B,defines an axis A that is oriented laterally with respect to theanterior-posterior direction and parallel to the first and second majorsurfaces 102, 104 of the body. Those skilled in the art will appreciatethat known design techniques may be employed to assure that rotation ofthe first gear 130A causes rotation of each of the first and secondanchoring elements 120A, 120B given the above-described constructionalrelationships.

The first gear aperture 132A extends toward and opens at at least one ofthe anterior and posterior sidewalls (in this case the anterior sidewall106). The first gear 130A includes first and second ends, the first ofwhich is directed toward the aperture opening at the anterior sidewall106. The first end of the first gear 130A includes a drive toolengagement feature that permits a drive rotational force to be appliedto the first gear 130A. (It is noted that the drive tool engagementfeature may alternatively or additionally be disposed on the second endof the first gear 130A.) The drive tool engagement feature isillustrated as a hex recess, but may include any of the known orhereinafter developed technologies, such as a star recess, a slot, aPhilips head recess, etc. The drive tool (not shown) may access andengage the first gear 130A through the aperture opening at the anteriorsidewall 106. The aperture 132A (possibly in combination with anotheraperture 132B) may also serve as engagement features for an insertiontool used by the surgeon to implant the device within the intervertebralspace.

The first gear 130A and the first gear aperture 132A may include aretention feature disposed at the opposing second end of the first gear130A. The retention feature permits the first gear 130A to rotate butprevents the first gear 130A from moving longitudinally (translating)through the first gear aperture 132A during deployment of the firstanchoring element 120A. By way of example, the retention featureincludes a throat 134 within the first gear aperture 132A and acorresponding neck 136 and head 138 at the opposite end of the firstgear 130A. The throat 134, neck 136 and head 138 cooperate to preventthe first gear 130A from moving longitudinally through the first gearaperture 132A.

As best seen on the exposed portion of the anchoring element 120D ofFIG. 4, the anchoring elements may each include a stop member 140, forexample, in the form of a head, at a proximal end thereof. Withappropriate multiplicities of diameters of the wall of the aperture forthe anchor 120D, the stop member 140 may permit the anchor 120D to slidethrough the associated aperture during deployment but prevent the anchor120D from exiting the body altogether.

A second gear 130B and associated aperture 132B (of similar constructionto that already described) may be disposed on the opposite lateral sideof the body to deploy the other anchors 120C, 120D.

Once the anchor elements 120 have been deployed, the one or more gearsmay be fixed in position by way of the gearing itself, which preferablywill not permit the anchor elements 120 to back out of their deployedstate. Alternatively, a set screw or any of the other known orhereinafter developed techniques may be used to fix the gearing inplace.

Reference is now made to FIGS. 5A and 5B, which illustrate analternative embodiment of an intervertebral prosthesis 100A of thepresent invention. Those skilled in the art will recognize similaritiesin the construction of the device 100A with respect to the device 100described earlier herein. The body of the device 100B includes first andsecond spaced apart major surfaces 102, 104 and anterior and posteriorsidewalls 106, 108 extending therebetween. The first major surface 102operates to engage an endplate of the first vertebral bone 10 of thespine, and the second major surface 104 operates to engage an endplateof the adjacent, second vertebral bone 20 of the spine. As in otherembodiments described herein, one or more anchoring elements 120A, 120B,120C, 120D may be deployed from within the body and engage one or moreof the vertebral bones 10, 20.

With reference to FIG. 5B, the trajectory Lt of the anchoring elements,such as anchoring element 120A is transverse to the longitudinal axis Loof the body. More particularly, the deployment direction Lt includes afirst substantial directional component Lp in a posterior direction ofthe body (toward the posterior sidewall 108). The deployment directionLt also includes a second substantial directional component Lop parallelto the longitudinal axis Lo of the spine. The trajectory −Lt (althoughnot shown in the drawing) of the second anchoring element 120B is alsotransverse to the longitudinal axis Lo of the body. That trajectoryincludes a first substantial directional component Lp in the posteriordirection of the spine, and a second substantial directional component−Lop parallel to the longitudinal axis Lo of the spine, but opposite tothe second substantial directional component Lop of the direction of thefirst anchoring element 120A. The transverse and opposite trajectoriesof the first and second anchoring elements 120A, 120B providesignificant anchoring strength.

Those skilled in the art will appreciate that known design techniquesmay be employed to assure that rotation of the gears 130A, 130B causesrotation of each of the first and second anchoring elements 120A, 120B,and the third and fourth anchoring elements 120C, 120D, respectively,given the above-described constructional relationships.

Reference is now made to FIGS. 6-9, which illustrate an alternativeembodiment of an intervertebral prosthesis 100B of the presentinvention. Those skilled in the art will again recognize similarities inthe construction of the device 100B with respect to the devices 100,100A described earlier herein. In this embodiment, at least one andpreferably a pair of anchoring elements 120A, 120B may be deployed atcompound trajectories from within the body and engage one or more of thevertebral bones 10, 20. Given the trajectories of the anchoring elements120A, 120B, a pair of apertures 110A, 110B extend between and through atleast one of the first and second major surfaces 102, 104 of the bodyand operate to permit osteo-inductive growth between the body of theprosthesis 100B and the one or more vertebral bones 10, 20.

With reference to FIG. 8, the trajectory Lt of the anchoring elements,such as anchoring element 120A, is transverse to the longitudinal axisLo of the body. More particularly, the deployment direction Lt includesa first substantial directional component Lp in a posterior direction ofthe body (toward the posterior sidewall 108), a second substantialdirectional component Lop parallel to the longitudinal axis Lo of thespine, and a third substantial directional component Ll in a lateraldirection with respect to the anterior-posterior direction of the spine.The trajectory −Lt of the second anchoring element 120B is alsotransverse to the longitudinal axis Lo of the body. That trajectoryincludes a first substantial directional component Lp in the posteriordirection of the spine, a second substantial directional component −Lopparallel to the longitudinal axis Lo of the spine, but opposite to thesecond substantial directional component Lop of the first anchoringelement 120A, and a third substantial directional component −Ll in alateral direction with respect to the anterior-posterior direction ofthe spine and opposite to the third substantial directional component Llof the first anchoring element 120A. These compound transverse andopposite trajectories of the first and second anchoring elements 120A,120B provide significant anchoring strength.

With reference to FIGS. 8-9, an example is illustrated as to how toimplement the deploying anchoring elements 120A, 120B of the device100B. In particular, the device 100B may include a gear 130 disposedwithin a gear aperture 132, where the gear 130 is disposed adjacent to,and in meshed, threaded communication with, the threaded shafts of thefirst and second anchoring elements 120A, 120B. The gear aperture 132,the first aperture 122A for the first anchoring element 120A, and thesecond aperture 122B for the second anchoring element 120B are locatedand oriented such that the apertures intersect over at least a portionthereof. As best seen in FIG. 9, the intersection of the gear aperture130, the first aperture 122A, and the second aperture 122B, defines anaxis B that is oriented transverse to the longitudinal axis of the body,transverse to the anterior-posterior direction of the body, andtransverse to the first and second major surfaces 102, 104 of the body.The gear 130 and the first and second anchoring elements 120A, 120B arein meshed, threaded communication at and along the direction (axis B) ofthe intersection.

In the illustrated example, the gear 130 is in the form of a helicalgear having a longitudinal orientation in an anterior-posteriordirection within the gear aperture 132. In this embodiment, thelongitudinal orientation of the gear 130 may be substantially parallelto the first and second major surfaces 102, 104 of the body. Thoseskilled in the art will appreciate that the threads of the gear 130 andthe threads of the first and second anchoring elements 120A, 120B may bereadily sized and shaped (in terms of pitch, depth, profile, etc.) suchthat rotation of the gear 130 causes rotation of the first and secondanchoring elements 120A, 120B in the proper rotational directions tothread the anchoring elements into the vertebral bones 10, 20.

Those skilled in the art will recognize that variations in the design ofthe device 100B are possible. For example, given the disclosure herein,one skilled in the art will appreciate that the trajectories of thefirst and second anchoring elements 120A, 120B may be reversed (at leastin the anterior-posterior direction), such that the deployment directionLt of the first anchoring element 120A includes a first substantialdirectional component La in an anterior direction of the body (towardthe anterior sidewall 106), a second substantial directional componentLp parallel to the longitudinal axis Lo of the spine, and a thirdsubstantial directional component Ll in a lateral direction with respectto the anterior-posterior direction of the spine. The trajectory −Lt ofthe second anchoring element 120B may include a first substantialdirectional component La in the anterior direction of the spine, asecond substantial directional component −Lp parallel to thelongitudinal axis Lo of the spine, but opposite to the secondsubstantial directional component Lp of the first anchoring element120A, and a third substantial directional component −Ll in a lateraldirection with respect to the anterior-posterior direction of the spineand opposite to the third substantial directional component Ll of thefirst anchoring element 120A.

Reference is now made to FIGS. 10-12, which illustrate an alternativeembodiment of an intervertebral prosthesis 100C of the presentinvention. Those skilled in the art will again recognize similarities inthe construction of the device 100C with respect to the devices 100,100A, and 100B described above. In this embodiment, at least one andpreferably a pair of anchoring elements 120A, 120B may be deployed atcompound trajectories from within the body and engage one or more of thevertebral bones 10, 20. In contrast to the device 100B, however, thisembodiment includes separate driving gears to deploy each of theanchoring elements 120A, 120B.

The trajectories Lt, −Lt of each of the anchoring elements 102A, 102B ofthe device 100C may be described in substantially the same way as thetrajectories of the device 100B (including the ability, withmodification, to be generally directed to the posterior direction asshown, or alternatively in the anterior direction).

With reference to FIG. 12, an example is illustrated as to how toimplement the deploying anchoring elements 120A, 120B of the device100C. In particular, the device 100C may include a first gear 130Adisposed within a first gear aperture 132A, where the first gear 130A isdisposed adjacent to, and in meshed, threaded communication with, thethreaded shaft of the first anchoring element 120A. The first gearaperture 132A and the first aperture 122A for the first anchoringelement 120A are located and oriented such that the apertures intersectover at least a portion thereof. As best seen in FIG. 11, theintersection of the first gear aperture 130A and the first aperture 122Adefines an axis C that is oriented transverse to the longitudinal axisof the body, transverse to the anterior-posterior direction of the body,and transverse to the first and second major surfaces 102, 104 of thebody. The first gear 130A and the first anchoring element 120A are inmeshed, threaded communication at and along the direction (axis C) ofthe intersection.

In the illustrated example, the first gear 130A is in the form of ahelical gear having a longitudinal orientation in an anterior-posteriordirection within the first gear aperture 132A. In this embodiment, thelongitudinal orientation of the first gear 130A may be substantiallyparallel to the first and second major surfaces 102, 104 of the body.Those skilled in the art will appreciate that the threads of the firstgear 130A and the threads of the first anchoring element 120A may bereadily sized and shaped (in terms of pitch, depth, profile, etc.) suchthat rotation of the first gear 130A causes rotation of the firstanchoring element 120A in the proper rotational direction to thread theanchoring elements into the vertebral bones 10, 20.

The construction of the second gear 130B, the second anchoring element120B, and the respective apertures 132B, 122B, therefor, are ofsubstantially similar characteristics, and thus a detailed discussionthereof will not be repeated.

Reference is now made to FIGS. 13-19, which illustrate a tool 200 forassisting the surgeon in implanting the device 100 in the patient'sspine. As will be discussed in more detail below, the surgeon may usethe tool 200 to simultaneously grasp the body of the device 100, placeit at the mouth of the intervertebral space, and apply force so that thedevice 100 achieves its final placement. Thereafter, an element of thetool 200 is manipulated by the surgeon to cause the one or moreanchoring elements 120 to deploy from within the body and engage one ormore of the vertebral bones 10, 20 in directions transverse to thelongitudinal axis Lo of the body and the spine.

With specific reference to FIGS. 13A and 13B, which are side and topviews, respectively, the tool 200 includes a handle 202 disposed at aproximal end, and a chuck 204 disposed at a distal end thereof. As willbe developed in more detail below, the chuck 204 is operable toreleasably engage the intervertebral stabilizer 100 such that thesurgeon may manipulate the position of the stabilizer 100 by way of thehandle 202 in order to urge the stabilizer 100 into the intervertebralspace.

The handle 202 includes a drive nut 206 operating to produce rotationaltorque in response to user-input. The rotational torque of the drive nut206 is transferred to one or more of first and second drive shafts 208,210, causing the dive shaft(s) to turn and produce rotational torque(s)at the distal end of the tool 200. More specifically, each of the firstand second drive shafts 208, 210 includes proximal and distal ends, theproximal ends being in communication with the drive nut 206, receivingrotational torque therefrom, and imparting rotational torques to therespective drive shafts about respective first and second axes A1, A2.The first and second drive shafts 208, 210 extend through, and arerotatable within, the chuck 204. The distal ends of the first and seconddrive shafts 208, 210 each include a respective drive head 212, 214.Each of the first and second drive heads 212, 214 are sized and shapedto engage a respective one of the first and second gears 130A, 130B ofthe intervertebral stabilizer 100. By way of example, the first andsecond drive heads 212, 214 may be of a hexagonal design, a star design,a slot design, a Philips-head design, etc. Thus, rotation of the drivenut 206 results in rotation and deployment of the anchoring elements 120of the intervertebral prosthesis 100.

Reference is now made to FIGS. 14 and 15, which are exploded views ofthe proximal and distal ends of the tool 200, respectively, inaccordance with one or more embodiments. The drive nut 206 operates toproduce rotational torque about a central axis, AC, which is laterallyoffset from each of the first and second axes A1, A2 of the first andsecond drive shafts 208, 210. The handle 202 further includes a maindrive gear 220, which is rotatable about the central axis AC, and iscoupled to, and receives the rotational torque from, the drive nut 206.The proximal ends of the first and second drive shafts 208, 210 eachinclude a pickup gear 222, 224 in meshed communication with the maindrive gear 220. Thus, each of the first and second pickup gears 222, 224receive rotational torque from the main drive gear 220, and impartrotational torque to the respective first and second drive shafts 208,210. By way of example, the main drive gear 220, and the first andsecond drive gears 222, 224 may be spur gears; however, any otherappropriate gear type and orientation are possible, such as helicalgears, worm gears, external and/or internal gears, etc.

Reference is now made to FIGS. 16-18, where FIG. 16 is a sectional viewof the tool 200 of FIG. 13A, taken through line 16-16, and FIGS. 17-18are enlargements of the distal and proximal ends of the sectional view,respectively. As best seen in FIG. 16, the tool 200 includes a centralhousing 230 extending generally from the handle 202 to the chuck 204.The central housing 230 operates to maintain proper orientation asbetween the handle 202 and the chuck 204 as well as other functions thatwill be discussed later herein. In addition, the tool 200 may include abushing section 232 that operates to maintain the respectiveorientations of the first and second drive shafts 208, 210. By way ofexample, the first and second drive shafts 208, 210 may be substantiallyparallel to one another along their lengths. In this regard, and withfurther reference to FIG. 15, the bushing section 232 may include a pairof apertures 232A, 232B, which permit the first and second drive shafts208, 210 to slide and rotate therein. As best seen in FIG. 18, theparallel relationship of the first and second drive shafts 208, 210 (andthus the respective axes A1, A2 thereof) are maintained via thestructures of the handle 202, the bushing 232, and the chuck 204. Inaddition the respective axes A1, A2 are both laterally offset from thecentral axis AC of the drive nut 206.

With specific reference to FIG. 17, the central housing 230 may includea retaining rod 234 extending therethrough and operating to couple theintervertebral prosthesis 100 to the chuck 204 during insertion thereofinto the spine. By way of example, the retaining rod 234 may include aproximal end coupled to the handle 202 and a distal end operating tocouple to the intervertebral prosthesis 100. The distal end of theretaining rod 234 may include a specific engagement feature 236 thatincludes structure suitable for connection to the intervertebralprosthesis 100. By way of example, the engagement feature 236 may bethreaded and capable of threading into a complementary threaded borewithin the intervertebral prosthesis 100. In this regard, the retainingrod 234 may extend through the handle 202 to the drive nut 206, suchthat the user (e.g., the surgeon) may couple the intervertebralprosthesis 100 to the tool 200 by way of rotating the drive nut 206.

Additionally or alternatively, the retaining rod 234 may operate as adrive shaft to deploy one or more anchors 120 from the intervertebralprosthesis 100. For example, the intervertebral prosthesis 100 mayinclude certain features illustrated in FIGS. 8-9, such as the centralgear 130 in meshed, threaded communication with, one or more of thethreaded shafts of the first and second anchoring elements 120A, 120B.In such an example, the retaining rod 234 may operate as a central driveshaft, where the proximal end thereof is coupled to the main drive gear220, receiving rotational torque therefrom, and imparting rotationaltorque to the central drive shaft about the central axis AC. The distalend of the central drive shaft may include a central drive head, whichoperates to engage the central gear 130 of the intervertebral prosthesis100. Thus, rotation of the drive nut 206 causes rotation of the centralgear 130 and deployment of one or more of the anchoring elements 120 ofthe intervertebral prosthesis 100.

Reference is now made to FIG. 19, which is an end view of the tool 200of FIGS. 13A and 13B showing alternative or additional features inaccordance with one or more further aspects of the invention. Inparticular, the first and second drive shafts 208, 210 lay in a plane OBthat is oblique to the longitudinal axis LO of the intervertebralprosthesis 100. This is advantageous in that, when two drive shafts areemployed (e.g., shafts 208, 210), the shafts may align with offset drivegears 130A, 130B, of the intervertebral prosthesis 100, such as isillustrated in FIGS. 10-12. Although the invention herein has beendescribed with reference to particular embodiments, it is to beunderstood that these embodiments are merely illustrative of theprinciples and applications of the present invention. It is therefore tobe understood that numerous modifications may be made to theillustrative embodiments and that other arrangements may be devisedwithout departing from the spirit and scope of the present invention asdefined by the appended claims.

1. An apparatus for inserting an intervertebral prosthesis within aspine of a mammal, comprising: a handle disposed at a proximal end ofthe tool and including a drive nut operating to produce rotationaltorque in response to user-input; a main drive gear rotatable about acentral axis, and coupled to, and receiving the rotational torque from,the drive nut; and a first drive shaft including proximal and distalends; the proximal end including a first pickup gear in meshedcommunication with the main drive gear, receiving rotational torquetherefrom, and imparting rotational torque to the first drive shaftabout a first axis, which is laterally offset from the central axis; andthe distal end of the first drive shaft including a first drive headwherein a distal end of the tool operates to engage the intervertebralprosthesis during implantation, and the first drive head operates toengage a first gear of the intervertebral prosthesis, such that rotationof the first gear causes rotation and deployment of a first anchoringelement of the intervertebral prosthesis.
 2. The apparatus of claim 1,further comprising a chuck disposed at the distal end of the tool andbeing sized and shaped to engage the intervertebral prosthesis duringimplantation, wherein the first drive shaft extends through the chucksuch that the first drive head operates to engage the first gear of theintervertebral prosthesis.
 3. The apparatus of claim 1, furthercomprising: a second drive shaft including proximal and distal ends; theproximal end including a second pickup gear in meshed communication withthe main drive gear, receiving rotational torque therefrom, andimparting rotational torque to the second drive shaft about a secondaxis, which is laterally offset from both the central axis and the firstaxis; and the distal end of the second drive shaft including a seconddrive head, wherein the second drive head operates to engage a secondgear of the intervertebral prosthesis, such that rotation of the secondgear causes rotation and deployment of a second anchoring element of theintervertebral prosthesis.
 4. The apparatus of claim 3, wherein thefirst and second drive shafts are substantially parallel to one another.5. The apparatus of claim 3, wherein the main drive gear and the firstand second drive gears are spur gears.
 6. The apparatus of claim 3,wherein: the first and second drive shafts lay in a plane that isoblique to a longitudinal axis of the intervertebral prosthesis; and theintervertebral prosthesis includes a body having first and second spacedapart major surfaces and at least anterior and posterior sidewallsextending therebetween, the first major surface for engaging an endplateof a first vertebral bone of the spine, and the second major surface forengaging an endplate of an adjacent, second vertebral bone of the spine,and the longitudinal axis extends substantially normal to the first andsecond major surfaces.
 7. The apparatus of claim 1, further comprising:a central drive shaft including proximal and distal ends; the proximalend coupled to the main drive gear, receiving rotational torquetherefrom, and imparting rotational torque to the central drive shaftabout the central axis; and the distal end of the central drive shaftincluding a central drive head, wherein the central drive head operatesto engage a central gear of the intervertebral prosthesis, such thatrotation of the central gear causes rotation and deployment of one ormore anchoring elements of the intervertebral prosthesis.
 8. Theapparatus of claim 1, further comprising a central housing, wherein thehandle is connecting to one end thereof and the chuck is connected to anopposite end thereof.
 9. The apparatus of claim 7, further comprising aretaining rod extending through the central housing and operating tocouple the intervertebral prosthesis to the chuck during insertionthereof into the spine.
 10. An apparatus for inserting an intervertebralprosthesis within a spine of a mammal, comprising: a handle disposed ata proximal end of the tool and including a drive nut operating toproduce rotational torque in response to user-input about a centralaxis; and a first drive shaft including proximal and distal ends; theproximal end in communication with the drive nut, receiving rotationaltorque therefrom, and imparting rotational torque to the first driveshaft about a first axis, which is laterally offset from the centralaxis; and the distal end of the first drive shaft including a firstdrive head, wherein the first drive head engages a first gear of theintervertebral prosthesis, such that rotation of the first gear causesrotation and deployment of a first anchoring element of theintervertebral prosthesis.
 11. The apparatus of claim 10, furthercomprising a chuck disposed at the distal end of the tool and beingsized and shaped to engage the intervertebral prosthesis duringimplantation, wherein the first drive shaft extends through the chucksuch that the first drive head operates to engage the first gear of theintervertebral prosthesis.
 12. The apparatus of claim 10, furthercomprising: a second drive shaft including proximal and distal ends; theproximal end being in communication with the drive nut, receivingrotational torque therefrom, and imparting rotational torque to thesecond drive shaft about a second axis, which is laterally offset fromboth the central axis and the first axis; and the distal end of thesecond drive shaft including a second drive head, wherein the seconddrive head operates to engage a second gear of the intervertebralprosthesis, such that rotation of the second gear causes rotation anddeployment of a second anchoring element of the intervertebralprosthesis.
 13. An apparatus, comprising: a tool for inserting anintervertebral prosthesis within a spine of a mammal, including: ahandle disposed at a proximal end of the tool and including a drive nutoperating to produce rotational torque in response to user-input; and afirst drive shaft including proximal and distal ends; the proximal endbeing in communication with the drive nut, receiving rotational torquetherefrom, and imparting rotational torque to the first drive shaftabout a first axis; and the distal end of the first drive shaftincluding a first drive head; and the intervertebral prosthesis,including: a body including first and second spaced apart major surfacesand at least anterior and posterior sidewalls extending therebetween,the first major surface for engaging an endplate of a first vertebralbone of the spine, and the second major surface for engaging an endplateof an adjacent, second vertebral bone of the spine, and the first andsecond major surfaces defining a longitudinal axis extendingsubstantially normal to said surfaces; a first aperture extending fromwithin the body, transversely with respect to the longitudinal axis, andopening at the first major surface; a first anchoring element disposedwithin the first aperture and including a threaded shaft having proximaland distal ends; and a first gear disposed adjacent to and in meshed,threaded communication with the threaded shaft of the first anchoringelement such that rotation of the first gear causes rotation of thefirst anchoring element, wherein the first drive head operates to engagethe first gear of the intervertebral prosthesis, such that a drivingrotational force on the first gear causes the first anchoring element torotate, deploy from the body, and thread into the first vertebral bonein a direction transverse to the longitudinal axis of the body and thespine.
 14. The apparatus of claim 13, wherein: the tool furthercomprises a second drive shaft including proximal and distal ends; theproximal end being in communication with the drive nut, receivingrotational torque therefrom, and imparting rotational torque to thesecond drive shaft about a second axis; and intervertebral prosthesisfurther comprises: (i) a second aperture extending from within the body,transversely with respect to the longitudinal axis, transversely withrespect to the first aperture and opening at the second major surface,(ii) a second anchoring element disposed within the second aperture andincluding a threaded shaft having proximal and distal ends, and (iii) asecond gear disposed adjacent to and in meshed, threaded communicationwith the threaded shaft of the second anchoring element such thatrotation of the second gear causes rotation of the second anchoringelement, wherein the second drive head operates to engage the secondgear of the intervertebral prosthesis, such that the first and secondanchoring elements operate to deploy from the body and thread into thefirst and second vertebral bones, respectively, in directions transverseto: (i) the longitudinal axis of the body, (ii) the spine, and (iii) toone another.
 15. An apparatus, comprising: a tool for inserting anintervertebral prosthesis within a spine of a mammal, including: ahandle disposed at a proximal end of the tool and including a drive nutoperating to produce rotational torque in response to user-input; and adrive shaft including proximal and distal ends; the proximal end beingin communication with the drive nut, receiving rotational torquetherefrom, and imparting rotational torque to the drive shaft about afirst axis; and the distal end of the drive shaft including a drivehead; and the intervertebral prosthesis, including: a body includingfirst and second spaced apart major surfaces and at least anterior andposterior sidewalls extending therebetween, the first major surface forengaging an endplate of a first vertebral bone of the spine, and thesecond major surface for engaging an endplate of an adjacent, secondvertebral bone of the spine, and the first and second major surfacesdefining a longitudinal axis extending substantially normal to saidsurfaces; one or more apertures extending from within the body,transversely with respect to the longitudinal axis, and opening at oneor more of the first and second major surfaces; one or more anchoringelements disposed within the apertures and including respective threadedshafts having proximal and distal ends; and at least one gear disposedadjacent to and in meshed, threaded communication with the threadedshafts of the one or more anchoring elements such that rotation of theat least one gear causes rotation of the one or more anchoring elements,wherein the drive head operates to engage the at least one gear of theintervertebral prosthesis, such that a driving rotational force on thegear causes the one or more anchoring elements to rotate, deploy fromthe body, and thread into one or more of the vertebral bones in adirection transverse to the longitudinal axis of the body and the spine.